Swiss cheese is one of the most difficult varieties of cheese to make. Control of the quality and composition of the milk, propagation and use of the essential bacterial starters and the details of manufacture are complicated procedures. Three species of bacteria have conventionally been used as starters during a fermentation period: these being a coccus culture, and a rod culture and a propionic acid forming microorganism. Usually Streptococcus thermophilus is used as the coccus culture; Lactobacillus bulgaricus or Lactobacillus lactis is used as the rod culture, and Proprionibacterium shermanii has been used as the propionic acid-forming microorganism. A milk clotting enzyme, such as rennet is also used and added in an amount such that a curd firm enough to cut is formed in about 30 minutes. The fermentation proceeds at a temperature of from about 88.degree. F. to about 94.degree. F. The curd is cut and worked for about 30 minutes to an hour. The curd is then heated over a period of about 30 minutes to a cooking temperature of between 120.degree. F. and 128.degree. F. The curd is stirred at the cooking temperature for about 30 minutes to an hour. Whey is then removed and the curd is processed into blocks for curing to produce Swiss cheese with typical eye formation. The total time required for fermentation, working and cooking is usually less than about 3 hours.
The Lactobacillus and Streptococcus starters produce lactic acid which aids in expelling the whey and contributes to the breakdown of the curd during ripening. The propionic acid forming microorganisms are largely responsible for the characteristic flavor and eye formation of Swiss cheese.
Swiss cheese manufacture is characterized by the use of temperatures during fermentation and cooking temperatures after fermentation; of from 88.degree. F. to 94.degree. F. and from 120.degree. F. to 128.degree. F., respectively.
The manufacture of cheese and cheese products from milk through preparation of a retentate by membrane processes, such as ultrafiltration and diafiltration, for removal of salts, lactose and water, has been taught in various patents and literature references. From the large variety of methods and procedures which have been proposed for the manufacture of cheese and cheese products from retentates, it is apparent that the physical chemistry of milk is complex and the interactions between the protein, fat, salts and other components of milk are affected by utilization of the retentate. It is also apparent that methods and procedures which have been proposed for treatment of a retentate vary in the manufacture of cheeses of differing varieties. For example, some procedures, such as disclosed in U.S. Pat. No. 4,820,530 U.S. patent application Ser. No. 649,838, filed on Sept. 11, 1984, to Moran et. al. and assigned to the same assignee as the present application, disclose the desirability of certain cheese make conditions to achieve the desired results. There is no teaching, however, in these prior art cheese make procedures as to a procedure for the manufacture of Swiss cheese from retentate without a whey draining step. U.S. Pat. No. 4,379,170 to Hettinga et al. discloses a process for making cheese, including Swiss flavored cheese wherein skim milk is concentrated, a portion of the skim milk is concentrated by ultrafiltration, and a portion of the concentrated skim milk is fermented. The concentrated skim milk, fermented concentrated skim and cream are mixed together in suitable proportions to provide a substrate suitable for the manufacture of cheese. The substrate is then reacted with a coagulant, such as rennet, to provide a coagulum. The coagulum is cut to provide curd and whey and the whey is drained. The Hettinga et al. patent, of course, does not teach a method for manufacture of Swiss cheese directly from a retentate without the use of a whey drawing step.
PCT Application No. WO82/01806 discloses a process which permits evaporation of water from fermented retentate. The process includes four steps: (1) selective concentration of milk to form a retentate; (2) increasing the ionic strength of the retentate by the addition of a salt, such as sodium chloride, so as to maintain it in the liquid phase during fermentation; (3) fermenting the retentate and (4) removing water from the fermented retentate to produce a cheese base containing substantially all the casein and whey proteins originally present in the milk.
A patent to Coulter, et al., entitled "Cheese Manufacture from Molecular Sieved Milk," issued Oct. 26, 1976, U.S. Pat. No. 3,988,481, teaches the preparation of cheese from milk which has been de-lactosed and de-watered by a process involving molecular sieving a standardized milk to separate and remove lactose and water-soluble minerals from the milk to render the milk substantially sugar-free, and adding a curd-forming agent to produce curd. The resulting curd is subjected to conventional handling without substantial syneresis to produce a cheese.
A patent to Stenne, entitled "Method for the Manufacture of Cheeses," issued Aug. 12, 1975, U.S. Pat. No. 3,899,596, discloses a process for the production of a cheese which comprises treating milk by ultrafiltration to obtain a product having at least some of the protein constituents of the milk, renneting the liquid product after inoculation with suitable ferments, and introducing a batch of the renneted liquid into a vertical chamber in which it is left to coagulate. The coagulum is cut into slabs which provide the end product cheese.
A patent to Maubois, et al., entitled "Manufacture of Cheese from Ultrafiltered Milk," issued Oct. 21, 1975, U.S. Pat. No. 3,914,435, teaches cheese made from heat-treated milk and without conventional draining of whey by a process which involves ultrafiltering of the milk to produce a concentrate having essentially the composition of cheese produced by conventional cheese making processes. The process enables the milk, after ultrafiltration, to be heat-treated without making the milk more difficult to coagulate with rennet, which difficulty normally occurs when milk is heated to higher temperatures.
A patent issued to Wargel, et al., entitled "Process and Products from the Manufacture of Cheese-flavored Products," issued June 13, 1981, U.S. Pat. No. 4,244,971, teaches the manufacture of cheeses and process cheeses, from ultrafiltered milk.
A patent entitled "Process for Preparing Cheese base," issued Aug. 30, 1983, to Rubin, et al., U.S. Pat. No. 4,401,679, discloses a process for preparing cheese base by concentrating milk through ultrafiltration, combined with diafiltration and evaporation, wherein the retentate from the ultrafiltration is inoculated with an acid culture before evaporation, and after evaporation acidification proceeds to completion after packaging.
Further, cheese base material has been taught by evaporating moisture from retentate under turbulent conditions to provide a lower moisture condition. Such a process is described in an article by Ernstrom, et al., entitled "Cheese base for Processing: A High-yield Product from Whole Milk by Ultrafiltration," published in the Journal of Dairy Science, Volume 63, 223-234 (1980). The article teaches a process wherein whole milk having normal pH, or acidified to a pH of 5.7, is concentrated by ultrafiltration to about 40 percent of the original milk weight and diafiltered at constant volume until a desired ratio of lactose to buffer capacity is established. Then the retentate is further concentrated by ultrafiltration to 20 percent of the original milk weight. The retentate is then inoculated with cheese starter and incubated to completely ferment the residual lactose, pH control being achieved by controlling the level of lactose from the diafiltration step of the process. The product is further concentrated in a swept-surface vacuum-pan evaporator or a Luwa evaporator. It is pointed out that the use of a batch evaporator is necessitated when the retentate, upon fermentation, curdles or coagulates, since such a product cannot be readily processed in any continuous-flow evaporator.
It is known to add salt during fermentation to prevent coagulation and this was understood many years ago. See: LeLait/November-December, 1974/No. 539/540. Further, it has been disclosed that salt in the retentate may facilitate evaporation as disclosed in an Australian Application, which is the subject of a published application under the Patent Cooperation Treaty WO32/01306, published June 10, 1982.
The prior art specifically teaches that addition of rennet or other coagulating enzymes to high-solids milk systems causes rapid coagulation and is a condition to be avoided during evaporation, since, according to the prior art, the evaporation is highly inefficient after coagulation occurs. On the other hand, the presence of coagulating enzymes may be desired, particularly in higher-solids cheese, to provide the conventional presence of para kappa casein by cleavage of kappa casein. The kinetics of enzymatic coagulation of milk is disclosed by Alfred Carlson, in a thesis published in 1982, at the University of Wisconsin, entitled "The Kinetics of Enzymatic Coagulation of Milk."
In the conventional making of cheese with rennet, the macro peptides formed by rennet action are lost in the whey with consequent reduction in yield and loss of nutritious milk protein material. Accordingly, it would be desirable to enjoy the benefit of rennet action while avoiding whey removal with consequent loss of macro peptides.
The prior art teaches many different steps in respect to the manufacture of cheeses and cheese products from milk retentates. Evaporation of milk retentates is a previously known technique, but the resultant product does not have desired Swiss cheese curd character. Also, much of the prior art is directed toward the manufacture of higher moisture or soft cheeses.
In summary, the prior art is not directed to the manufacture of improved Swiss cheese, despite its many teachings relating to the manufacture of cheeses and cheese products from retentates derived from milk. There has been a lack of a commercial process for producing Swiss cheese from milk utilizing a retentate and an evaporating step.
It is a principal object of this invention to provide a Swiss cheese from a milk retentate followed by evaporation, the cheese having a typical Swiss cheese flavor, body and texture characteristics.
A further object of this invention is to provide Swiss cheese from milk which is stable and does not oil-off, and is manufactured by processing a milk retentate with evaporation.
Another object of the invention is to provide a process for the manufacture of Swiss cheese in which the milk proteins have been subjected to the action of a milk clotting enzyme but which process avoids loss of macro peptides.
Still further objects and advantages of the invention will become apparent by reference to the following description.